For some time, processes have been employed to heat underground formations containing viscous hydrocarbon deposits, thereby lowering the viscosity of the petroleum contained within and providing a driving force to assist in the recovery of these viscous hydrocarbons. The use of horizontal drilling technology for viscous hydrocarbon recovery is well-established. An large area of contact between the wellbore and the formation can be achieved by drilling wells with a substantially horizontal component (typically, 300 to 2,000 meters). This large contact area allows the formation to be heated more efficiently by injection of a heated fluid, thereby reducing the injection pressure required to heat the formation to the minimum temperature required for viscous hydrocarbon recovery. Heating the viscous hydrocarbons within a formation reduces their viscosity, and gravity assists the downward flow of these hydrocarbons within the formation. This recovery mechanism has been known as SAGD (Steam Assisted Gravity Drainage) process and has been employed in recovering viscous hydrocarbons from oil sands over the last 20 years. Since gravity is only drive force behind the SAGD process, hydrocarbon recovery is relatively slow due to slow lateral growth of the heat chamber. To enhance the process, a new drive mechanism for improved lateral expansion of the heat chamber is needed.
In certain geographic areas, the cost associated with gravity-assisted hydrocarbon recovery is increased due to a lack of water for steam generation, or increased cost of the fluid used for injection. What is needed are methods to maximize the efficiency of gravity-assisted viscous hydrocarbon recovery from underground formations by recovering and recycling the heated fluid that is injected during the process.